1. Field of the Invention
The present invention relates to a sheet conveying apparatus and an image forming apparatus, and particularly to the construction of a door opened when the sheet jam or the like has occurred in a sheet conveying path.
2. Description of the Related Art
A conventional image forming apparatus such as a copying machine or a printer is provided with a sheet conveying path for conveying a sheet. In some cases, this sheet conveying path is designed such that when the sheet jam has occurred, an openable and closable door provided in an apparatus main body is opened so that the sheet can be taken out.
As such a sheet conveying apparatus, there is one in which for example, a part of a sheet conveying path for conveying the sheet to an image forming portion is provided in the door and when jam clearance or the like is to be effected, this door is opened to thereby open the sheet conveying path and make it easy to effect jam clearance or the like.
As a construction in which the door is opened and closed as described above, there is one as disclosed in Japanese Patent Application Laid-Open No. 2001-146339 wherein a door is slidden to be opened and closed, or one as disclosed in Japanese Patent Application Laid-Open No. 2005-082307 wherein a door is opened and closed in a vertical direction by a hinge. There is also one as disclosed in Japanese Patent Application Laid-Open No. H11-231594 wherein a door is opened and closed in a horizontal direction.
Description will first be made of the construction of an image forming apparatus provided with such a conventional sheet conveying apparatus.
FIG. 11 of the accompanying drawings is a perspective view of such a conventional image forming apparatus.
In FIG. 11, in the upper portion of the image forming apparatus main body (hereinafter referred to as the apparatus main body) 51 of the image forming apparatus 50, there is provided an original reading portion 41 having an image sensor or the like for applying light to an original, and converting reflected light into a digital signal. Also, there are provided a plurality of stages of sheet supplying cassettes 52a, 52b, 52c and 52d containing therein sheets to be supplied to an image forming portion provided in the interior of the apparatus main body 51 for forming an image on the sheet.
The interior of the apparatus main body 51 will now be schematically described with reference to FIG. 12 of the accompanying drawings. Provision is made of a sheet conveying apparatus 53 for conveying the sheet, and first and second discharging portions 58A and 59A. By the sheet conveying apparatus 53, the sheet contained in the sheet supplying cassettes 52a, 52b, 52c and 52d, after images have been formed thereon, are discharged to the first discharging portion 58A or the second discharging portion 59A by being changed over by a flapper 61.
In the image forming portion, an image transferred to an intermediate transfer belt 63 is transferred to the sheet by a secondary transfer roller 56a in a secondary transferring portion 56. Further, the sheet to which the toner image has transferred is heated and pressurized in a fixing portion 57 comprising a pair of fixing rollers 57a and 57b, whereby the toner image thereon is fixed. The sheet S on which the toner image has been fixed is conveyed by a pair of first conveying rollers 5 constituted by rollers 5a and 5b. 
In FIGS. 11 and 12, a first door 1 is openably and closably provided with a rotation center shaft 4 (FIG. 15) provided so that the axis thereof may extend in a vertical direction on the rear side of a side of the apparatus main body 51 as a fulcrum. Also, on this first door 1, there are disposed a driven registration roller 62b constituting a pair of registration rollers 62 (a drive registration roller 62a and a driven registration roller 62b), the secondary transfer roller 56a and a roller 5b constituting a pair of first conveying rollers 5. Further, on this first door 1, there are mounted guide members 101a, 102a and 103a constituting first, second, third and fourth conveying paths 101, 102, 103 and 104, and a guide member 104a shown in FIG. 16 of the accompanying drawings which will be described later. Thereby, when the first door 1 is opened, the first, second, third and fourth conveying paths are opened and jam clearance can be effected easily. The first, second, third and fourth conveying paths 101, 102, 103 and 104 are vertically arranged.
A second door 11 above and adjacent to the first door 1 is openably and closably provided with a rotation center shaft 14 provided so that the axis thereof may extend in a vertical direction on the rear side of a side of the apparatus main body 51 as s fulcrum. Also, on this second door 11, there are disposed a roller 15b constituting a pair of second conveying rollers 15, and rollers 58a and 59a constituting pairs of first and second discharge rollers 58 and 59. Further, on this second door 11, there is mounted one guide member 105a constituting a fifth conveying path 105 shown in FIG. 16 which will be described later. Thereby, when the second door 11 is opened, the fifth conveying path 105 is opened and jam clearance can be effected easily.
Now, FIG. 13 of the accompanying drawings shows the construction of the inner wall surface side of the first door 1 and the second door 11. FIG. 13 shows the lock portion 1A of the first door 1 and the lock portion 11A of the second door 11. Here, the lock portion 1A of the first door 1 and the lock portion 11A of the second door 11 are provided with hooks 1a and 11a provided on the first and second doors 1 and 11, respectively, and latches 2 and 12 disengageably engaged with the hooks 1a and 11a, respectively.
These latches 2 and 12 have latch portions 2a and 12a disengageably engaged with the hooks 1a and 11a, respectively, lever portions 2b and 12b, and rotary shafts 2c and 12c, and are urged in the direction indicated by the arrow A about the rotary shafts 2c and 12c by urging means (not shown).
The latch portions 2a and 12a of the latches 2 and 12 are brought into engagement with the hooks 1a and 11a, whereby the first and second doors 1 and 11 can be fixed at positions forming first, second, third, fourth and fifth conveying paths 101, 102, 103, 104 and 105 which are sheet conveying paths. The pairs of first and second conveying rollers 5 and 15 are adapted to be urged in the direction indicated by the arrow C in FIG. 12 by urging means (not shown) and brought into pressure contact with each other when the first and second doors 1 and 11 have been fixed at the positions forming the conveying paths 101, 102, 103, 104 and 105.
Also, as shown in FIG. 11, on the front sides of the first and second doors 1 and 11, there are provided releasing buttons 3 and 13 for releasing the locking of the lock portions 1A and 11A. By depressing these releasing buttons 3 and 13, the latch portions 2a and 12a can be released from the hooks 1a and 11a, respectively. These releasing buttons 3 and 13 are outwardly urged by urging means (not shown).
Description will now be made of the operation of clearing the jammed sheet S in the conventional sheet conveying apparatus 53 of such a construction.
When as shown, for example, in FIG. 12, the sheet S is jammed at a position nipped by the pairs of first and second conveying rollers 5 and 15, the releasing button 3 is depressed in the direction indicated by the arrow D as shown in FIG. 14A so that the first door 1 may first be opened. When the releasing button 3 is thus depressed, the projection 3a of the releasing button 3 presses the lower portion 2b of the latch 2 urged in the direction indicated by the arrow A. Thereby, as shown in FIG. 14B of the accompanying drawings, the latch 2 is rotated in the direction indicated by the arrow E about the rotary shaft 2c, and when the latch 2 is thus rotated in the direction indicated by the arrow E, the engagement between the latch portion 2a and the hook portion 1a of the first door 1 is released.
Thereby, the first door 1 is rotated in the direction indicated by the arrow F about the rotation center shaft 4, as shown in FIG. 15, by the reaction force of urging means (now shown) urging the pair of first conveying rollers 5 in the direction indicated by the arrow C at the positions forming the first to fourth conveying paths 101, 102, 103 and 104. As the result, the first to fourth conveying paths 101, 102, 103 and 104 are opened and the pressure contact between the pair of first conveying rollers 5 (5a and 5b) is released.
Next, the second door 11 is opened. Again in this case, when the releasing button 13 is depressed, as in the case of the first door 1, the engagement between the latch portion 12a and the hook portion 11a of the second door 11 is released. Thereby, the second door 11 is rotated in the direction indicated by the arrow F, as shown in FIG. 16, by the reaction force of the urging means (not shown) urging the pair of second conveying rollers 15 at a position forming the fifth conveying path 105, and opens the fifth conveying path 105. As the result, the pressure contact between the pair of second conveying rollers 15 is released.
When the first and second doors 1 and 11 are thus opened, the pressure contact between the pair of first and second conveying rollers 5 and 15 is released and therefore, the jammed sheet S can be cleared easily.
After the jammed sheet S has been cleared, the first and second doors 1 and 11 are rotated in the direction indicated by the arrow G and closed, as shown in FIG. 17 of the accompanying drawings. When the first and second doors 1 and 11 are thus closed, the hooks 1a and 11a rotate the latches 2 and 12 urged in the direction indicated by the arrow A by the urging means (not shown) in the direction indicated by the arrow E, and are again engaged with the latch portions 2a and 12a of the latches 2 and 12, respectively.
By the hooks 1a and 11a being thus engaged with the latch portions 2a and 12a of the latches 2 and 12, respectively, the first and second doors 1 and 11 are fixed at the positions forming the first to fifth conveying paths 101, 102, 103, 104 and 105. Thereby, the pairs of first and second conveying rollers 5 and 15 are pressurized in the direction indicated by the arrow C indicated in FIG. 12 by the urging means (not shown), and the preparation for the conveyance of the next sheet is completed.
Now, in such a conventional sheet conveying apparatus and image forming apparatus, as already described, each door is opened before jam clearance is done and therefore, the releasing means (releasing button 13) for releasing the fixing means (lock means 1A and 11A) of the respective doors 1 and 11 is necessary for each door. However, in a case where the releasing means are provided on the doors 1 and 11, each time the doors 1 and 11 are opened, the respective releasing means must be operated, and the jam clearing operation has been cumbersome. So, as a countermeasure for simplifying the jam clearing operation, the portion opened in the jam clearance is made into a door long in the conveyance direction of the sheet. For example, as shown in FIG. 18 of the accompanying drawings, there is conceivable a method of making the two doors 1 and 11 into a single door 31.
However, when the two doors are thus made into a single door, each of the fixing means and the releasing means may be single, but the rollers 5a and 15a constituting the pairs of conveying rollers 5 and 15, respectively, are disposed on the single door 31. Therefore, when the door 31 is to be closed, the operating force is increased by the reaction force of the urging means for urging the pair of rollers.
That is, when as shown in FIG. 17, the force with which the first door 1 is closed is defined as F1, and the force with which the second door 11 is closed is defined F2, the force F3 with which the door 31 long in the conveyance direction shown in FIG. 19 of the accompanying drawings is closed becomes F3=F1+F2, and the operating force is increased. This has led to the problem that operability is bad.